EPOW - Ecology Picture of the Week

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A Most Unusual Fern

Credit & Copyright:  Dr. Bruce G. Marcot
  

Explanation:  A typical fern this is not.  Older fronds are lobed, like leaves of white oak.  Veins spread from the stem, like maples.  The tissue is thin, filmy, and small -- reaching only 2-4 inches (5-10 cm) in height, like liverworts.  What do we have here? This is a kidney fern, a common denizen of the forest floor found throughout New Zealand.  This species is endemic to New Zealand -- found nowhere else in the world.   Kidney ferns are so-named because of the kidney shape of the fronds.  It belongs to the very diverse "filmy fern" family that boasts nine genera and 600 species.       Local Maori names for kidney ferns include kopakopa, raurenga, and kōnehu. The Maori used kidney ferns fronds to scent oil.    Efforts have been made since the 1930s to cultivate kidney ferns, but propagation is very difficult.  It is best to leave them growing wild and enjoy them in their natural environment. In fact, some studies have demonstrated that presence of such ferns can be used as indicators of regions of high biodiversity (Lehmann et al. 2002).    In dry weather, the fronds curl up and die back, but renew themselves with the next rainfall. These light green fronds, however, may be new growth just appearing from the typical tangle of rhizomes that enmesh the forest floor. The web of rhizomes, in fact, may in turn  help to trap dead leaves and other organic matter that slowly decay like time-release sources of nutrients for the trees and other plants.    Kidney ferns often grow in dense mats and prevent competition from other plants by emitting chemicals that inhibit the growth of seedling roots. This suppression activity is referred to as allelopathy, and occurs in a surprisingly wide array of plant species in environment as diverse as deserts and these New Zealand rainforests.      Information:      Lehmann, A., J.R. Leathwick, and J.McC. Overton.  2002.  Assessing New Zealand fern diversity from spatial predictions of species assemblages.  Biodiversity & Conservation 11(12):2217-2238.